Nerve cell structures in circumscribed regions of the brain are pathologically, e.g. excessively synchronously, active in patients with neurological or psychiatric diseases such as Parkinson's disease, essential tremor, tinnitus, dystonia or obsessive compulsive disorders. In this case, a large number of neurons synchronously form action potentials, i.e. the participating neurons fire excessively synchronously. In a healthy person, in contrast, the neurons fire with a different quality, i.e. in an uncorrelated manner, in these brain sectors.
Stimulation techniques have been developed for treating such diseases which directly counteract pathologically synchronous neural activity. In particular the coordinated reset (CR) stimulation is in this respect characterized by great therapeutic effectiveness and reliability (cf. e.g. “A model of desynchronizing deep brain stimulation with a demand-controlled coordinated reset of neural subpopulations” by P. A. Tass, published in Biol. Cybern. 89, 2003, pages 81 to 88). The CR stimulation can be realized with different stimulus modalities, e.g. by means of electrical stimulation or sensory, e.g. acoustic, stimulation. The non-invasive stimulation processes and apparatus are particularly promising since they are much lower in side effects and are less expensive (and are thus accessible for a larger number of patients).
It is important for the effectiveness of the CR stimulation that the different sites in the brain or spinal cord which are stimulated by the stimulation lie in the neural population to be stimulated (or, in invasive CR stimulation, in the fiber bundle to be stimulated). In invasive CR stimulation, the ideal localization of the implanted electrode is ensured within the framework of the surgical planning, inter alia via detailed anatomical information, e.g. from magnetic resonance imaging examinations.
In the non-invasive stimulation processes, in contrast, the selection of the ideal stimulation sites in the brain or spinal cord which corresponds to a calibration of stimulation parameters, e.g. the pitches of the therapeutic tones in acoustic CR stimulation, or to a calibration of the localization of the different non-invasive actuators (e.g. the placement of the vibro-tactile stimulators on the skin in relation to the affected body part), is a problem yet to be solved. Time-consuming trial and error does not guarantee the ideal effectiveness of the non-invasive CR therapy since, on the one hand, not all possible stimulation sites in the brain are systematically developed and tested and, on the other hand, the patients are stressed by long examinations so that the cooperation of the patients naturally suffers and the results of the test become worse.